1. Field of the Invention
The present invention relates to a method for detection of oil mist and apparatus therefor in which an oil mist in a noninflammable gas is formed into a deposit form by heat decomposition, an accumulated amount of the decomposed deposit is detected as an electric resistance variation, and the oil mist amount is detected from the electric resistance value.
2. Description of the Prior Art
Recently, a sealed reciprocating engine such as a Stirling engine is provided with a seal portion so that a cylinder having a piston slidably encased therein is sealed relative to a guide rod for transmitting a reciprocating motion of the piston outside the cylinder, and oil is used in the seal portion. This gives rise to a problem in that oil leaked from the seal portion is atomized to contaminate the interior of the cylinder to impede the reciprocating motion of the piston. It is therefore necessary to measure the oil mist within the cylinder during the reciprocating motion of the piston.
A conventional measuring device has used a piezoelectric element as an oil mist measuring sensor, for example, such as a piezo-balance dust meter. For this reason, it is not possible to arrange the device within the cylinder in which pressure is varied to directly measure the oil mist. In other words, the gas within the cylinder is subjected to sampling to make pressure constant, after which the mist is indirectly measured in a chamber separately from the cylinder. This poses disadvantages that the measuring accuracy is not obtained and a pipe for sampling is required to unavoidably increase the size of the measuring device.
A specific embodiment of prior art will be described hereinafter with reference to the drawings.
FIG. 6 shows a Stirling engine 10 which converts energy of a high temperature and high pressure gas into a turning force. Four cylinders 11 (including those not shown) are symmetrically provided. Each cylinder 11 has a piston 12 arranged therein, and an expansion chamber 13 and a compression chamber 14 are formed on opposite ends, respectively, thereof. The expansion chamber 13 and compression chamber 14 are communicated with heat exchangers 15a and 15b, respectively, which are working as gas supply sources.
Each piston 12 has a guide rod 16 to transmit a reciprocating motion of the piston 12 outside the cylinder 11 through a rod seal 17. The guide rod 16 has a guide piston 18 connected thereto which is slidably moved within a guide cylinder 19. Each guide piston 18 is brought into engagement with a rotational oblique swash plate 20, which has a rotational shaft 21.
A helium gas is supplied to the engine 10 constructed as described above, and the piston 12 is periodically reciprocated within the cylinder 11.
This reciprocating motion is transmitted through the guide rod 16, and the guide pistons 18 are also reciprocated with a predetermined phase difference from each other. With this, the rotational oblique plate 20 in engagement with the guide piston 18 is rotated, which rotation is transmitted outside through the rotational shaft 21.
Hereinafter, the construction of the rod seal 17 for maintaining the cylinder 11 airtight relative to the guide rod 16 will be described with reference to FIG. 6.
Around the guide rod 16 are arranged a gas seal 26, an intermediate chamber 25 in communication with the compression chamber 14, an oil scraper 22, a liquid chamber 23 and an oil seal 24 in that order from the compression chamber 14. The liquid chamber 23 is brought into communication with the top of the oil scraper 22 through an oil tank 27.
Since oil is used for the purpose of sealing, oil in the liquid chamber 23 possibly leaks into the compression chamber 14 through the oil scraper 22, the intermediate chamber 25 and the gas seal 26. Therefore, in the engine 10, oil is distributed in the form of mist into the compression chamber 14.
This oil mist is adhered to inner walls of pipes of the heat exchanger 15a through a pipe which connects oil on the heat exchanger 15a with the compression chamber 14. As a result, the inner walls of the pipe becomes decomposed due to the high temperature of the heat exchanger 15a.
As the oil mist accumulates on the inner walls of the pipe, a gas flowpassage of the pipe is naturally blocked to deteriorate the efficiency of heat exchange of He gas or the like and to cause the efficiency of the compressor itself to be deteriorated.
Furthermore, when the efficiency of a filter 28 deteriorates, the oil mist is distributed in the form of a mist into the compression chamber 14 through the oil scraper 22, the intermediate chamber 25 and the filter 28, in a manner similar to that as previously described.
In view of the foregoing, it is important to detect concentration of the oil mist within the compression chamber 14 for the purpose of maintaining the performance of the engine 10.